staging: Core files for the DWC2 driver

The core code provides basic services for accessing and managing
the DWC_otg hardware. These services are used by both the Host
Controller Driver and (in future) the Peripheral Controller Driver.

Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>